Lipoteichoic acid (LTA)-Glucan complexes in dental plaque may be important for the expression of the cariogenic potential of S. mutans. LTA levels were measured in dental plaque samples taken from monkeys that were maintained on a high sucrose diet. The solid phase of the plaque contained most of the LTA whereas the liquid phase contained mainly deacylated-LTA. Radiolabeled LTA and deacylated-LTA were highly purified from Staph. aureus cells and culture fluids. Antibody to the LTA preparation gave a hemagglutination titer of 8000 with LTA purified from S. mutans strain BHT. Because of the immunological cross reactivity and the chemical similarities of the LTAs from some oral streptococci, lactobacilli and staphylococci the LTA preparations from Staph. aureus are also used in studies on the role of LTA in dental plaque formation. -Hybridoma cells lines have been established that produce monoclonal antibodies that react with purifed glucosyltransferase. The specificity of these antibodies for GTF and their use in the preparation of pure GTF for caries vaccine studies are under investigation.